Display panel and fabricating method thereof

ABSTRACT

A display panel and a fabricating method thereof are provided. The display panel includes: a substrate; and an array of pixels on the substrate, each pixel having a sub-pixel region and a photosensitive region, wherein the sub-pixel region includes a light emitting structure; the photosensitive region is configured to sense light emitted by the light emitting structure and reflected by a finger; and the photosensitive region includes a photosensitive thin film transistor having a vertical channel with respect to the substrate.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application is the U.S. national phase of PCT ApplicationNo. PCT/CN2019/081888 filed on Apr. 9, 2019 which is based on and claimspriority from Chinese Patent Application No. 201811012529.X, filed onAug. 31, 2018, the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

Embodiments of the present disclosure relate to a display panel and amethod of fabricating the same.

BACKGROUND

In the field of display, organic light-emitting diode (OLED) displaypanels have the characteristics of self-luminous, high contrast, lowpower consumption, wide viewing angle, fast response, flexible panel,wide temperature range, simple manufacturing process, etc., and thushave a good prospect of development. With the development of fingerprintrecognition technology, how to apply fingerprint recognition technologyto OLED display panels is a problem that has attracted much attention inthe industry.

SUMMARY

A display panel and a fabricating method thereof are disclosed.

According to a first aspect of the present disclosure, there is provideda display panel, the display panel including: a substrate; and an arrayof pixels on the substrate, each pixel having a sub-pixel region and aphotosensitive region, wherein the sub-pixel region includes a lightemitting structure; the photosensitive region is configured to senselight emitted by the light emitting structure and reflected by a finger;and the photosensitive region includes a photosensitive thin filmtransistor having a vertical channel with respect to the substrate.

The display panel may further include an insulating layer over thephotosensitive thin film transistor, and the light emitting structuremay be disposed over the insulating layer.

The photosensitive thin film transistor may include a gate electrode, agate insulating layer, a first electrode, an active layer, and a secondelectrode sequentially formed over the substrate.

The active layer may include a photosensitive layer.

The photosensitive layer may include a material ofpoly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C 61-butyric acid methylester (PCBM) composite.

The active layer may further include a semiconductor layer between thephotosensitive layer and the first electrode.

The semiconductor layer may includedinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) or pentacene.

A material of the first electrode may be a porous semiconductorelectrode material.

A material of the first electrode may be carbon nanotubes.

A material of the second electrode may be a transparent conductivematerial.

The photosensitive region may further include a first electrode leadelectrically connected to the first electrode; and the first electrodemay include a first portion and a second portion, the first portioncovering the first electrode lead with respect to the substrate, thesecond portion and the first electrode lead being arranged side by sidewith respect to the substrate.

The sub-pixel region may further include a first transistor, and asource or a drain of the first transistor may be electrically connectedto a first electrode of the light emitting structure.

A gate of the first transistor may be in a same layer as the gateelectrode of the photosensitive thin film transistor.

The photosensitive region may further include a second electrode leadelectrically connected to the second electrode of the photosensitivethin film transistor, and the second electrode lead may be in a samelayer as the source or the drain of the first transistor.

The photosensitive thin film transistor may be distal from the substraterelative to an active layer of the first transistor.

The sub-pixel region may include a plurality of sub-pixels, eachsub-pixel having a size substantially equal to a size of thephotosensitive region.

The display panel may further include a filter layer over the secondelectrode of the photosensitive thin film transistor, the filter layercovering the photosensitive thin film transistor.

According to a second aspect of the present disclosure, there isprovided a method of fabricating a display panel, the method including:providing a substrate; and forming an array of pixels on the substrate,each pixel having a sub-pixel region and a photosensitive region;wherein the sub-pixel region includes a light emitting structure; thephotosensitive region is configured to sense light emitted by the lightemitting structure and reflected by a finger; and the photosensitiveregion includes a photosensitive thin film transistor having a verticalchannel with respect to the substrate.

The method may further include forming an insulating layer over thephotosensitive thin film transistor; and forming the light emittingstructure over the insulating layer.

The method may further include forming the photosensitive thin filmtransistor by sequentially forming a gate electrode, a gate insulatinglayer, a first electrode, an active layer, and a second electrode overthe substrate.

BRIEF DESCRIPTION OF DRAWINGS

A more particular description of the embodiments will be rendered withreference to specific embodiments illustrated in the appended drawings.Given that these drawings depict only some embodiments and are nottherefore considered to be limiting in scope, the embodiments will bedescribed and explained with additional specificity and details throughthe use of the accompanying drawings, in which:

FIG. 1A is a schematic plan view of a display panel according to anembodiment of the present disclosure;

FIG. 1B is another schematic plan view of the display panel;

FIG. 2 is a partial cross-sectional view of a fingerprint recognitionarea of the display panel in FIG. 1A or FIG. 1B;

FIG. 3A is a schematic diagram of a pixel structure in the fingerprintrecognition area;

FIG. 3B is a schematic diagram of a photo-sensing circuit provided by anembodiment of the present disclosure;

FIG. 3C is a schematic diagram of another photo-sensing circuit providedby an embodiment of the present disclosure; and

FIGS. 4A-4E are diagrams illustrating a process of a method offabricating a display panel according to an embodiment of the presentdisclosure.

DETAILED DESCRIPTION OF EMBODIMENTS

The disclosure will be described hereinafter with reference to theaccompanying drawings, which illustrate embodiments of the disclosure.The described embodiments are only exemplary embodiments of the presentdisclosure, but not all embodiments. Other embodiments may be obtainedby a person of ordinary skill in the art based on the embodiments of thepresent disclosure without creative efforts, and are within the scope ofthe present disclosure.

References throughout the disclosure to “one embodiment”, “anembodiment”, “an example”, “some embodiments”, or similar language meanthat a particular feature, structure, or characteristic described inconnection with the embodiment is included in at least one embodiment.Thus, appearances of the phrases “in one embodiment”, “in anembodiment”, “in some embodiments”, and similar language throughout thedisclosure may, but do not necessarily, all refer to the sameembodiment(s), but mean “one or more embodiments”. These may or may notinclude all the embodiments disclosed.

Unless otherwise defined, technical terms or scientific terms used inthe embodiments of the present disclosure should be construed in theordinary meaning of the person of ordinary skill in the art.

The terms “first”, “second” and similar terms used in the presentdisclosure do not denote any order, quantity, or importance. They aremerely used for references to relevant devices, components, proceduralsteps, etc. These terms do not imply any spatial or chronologicalorders, unless expressly specified otherwise. For example, a “firstdevice” and a “second device” may refer to two separately formeddevices, or two parts or components of the same device. Similarly, a“first step” of a method or process may be carried or performed after,or simultaneously with, a ‘second step”.

The terms “comprising”, “including”, “having”, and variations thereofmean “including but not limited to”, unless expressly specifiedotherwise.

An enumerated listing of items does not imply that any or all of theitems are mutually exclusive, unless expressly specified otherwise. Theterms “a”, “an”, and “the” also refer to “one or more” unless expresslyspecified otherwise.

The words “connected” or “connection” and the like are not limited tophysical or mechanical connections, but may include electricalconnections, whether direct or indirect.

The words “over” is used only to indicate that a layer's relativeposition with respect to another layer, which means that the layer islocated further from the substrate than the other. This does notnecessarily require contact of the two layers, nor does it require thelayer fully or partially covering the other layer.

A display panel may be provided with fingerprint recognition functionwith an external structure or an in-display structure. The externalstructure refers to attaching a fingerprint recognition module tosomewhere outside a display area of the display panel. Such structurerequires additional preparation of a fingerprint recognition module (forexample, a capacitive fingerprint recognition module), and results in abulky final product. The in-display structure refers to the integrationof the fingerprint recognition module into the display panel, and suchstructure may realize fingerprint recognition under the screen. However,since the in-display structure may have compatibility issues with themanufacturing process of the display panel, how to produce a fingerprintrecognition module having high light responsivity and highsignal-to-noise ratio and how to optimize the manufacturing process areissues to be considered.

At least one embodiment of the present disclosure provides a displaypanel and a method of fabricating the same. The display panel integratesa photosensitive region in a display screen, and the photosensitiveregion is formed by using a photosensitive thin film transistor having avertical channel. The in-display structure achieves fingerprintrecognition under the screen, or full-screen fingerprint recognition. Inaddition, the photosensitive thin film transistor has a relatively largephotosensitive area (aperture ratio) and a relatively short channellength. Thus, the light responsivity and signal-to-noise ratio of thedisplay panel may be improved.

FIG. 1A is a schematic plan view of a display panel 10 according to anembodiment of the present disclosure; FIG. 1B is another schematic planview of the display panel; and FIG. 2 is a partial cross-sectional viewof a fingerprint recognition area of the display panel in FIG. 1A orFIG. 1B. For clarity purpose, only a portion of one sub-pixel region ofthe fingerprint recognition area is shown in FIG. 2. Referring to FIG.1A, FIG. 1B and FIG. 2, the display panel 10 includes a plurality ofgate lines 11, a plurality of data lines 12, and a plurality ofsub-pixel regions 100 arranged in an array. The plurality of gate lines11 and the plurality of data lines 12 intersect to define a plurality ofpixel regions, and the plurality of sub-pixel regions 100 are arrangedin the plurality of pixel regions in one-to-one correspondence. Each ofthe sub-pixel regions 100 includes a light emitting structure 110 and apixel circuit that drives the light emitting structure 110 to emitlight.

The display panel 10 includes a display area 20 that includes afingerprint recognition area 30. The fingerprint recognition area 30 maybe part or all of the display area 20.

For example, the display panel 10 is an organic light emitting diode(OLED) display panel, and the light emitting structure 110 is an organiclight emitting diode. For example, the pixel circuit includes aconventional 2T1C pixel circuit, and in various embodiments, it mayfurther include a compensation circuit that includes an internalcompensation circuit or an external compensation circuit. Thecompensation circuit may include a transistor, a capacitor, or the like.The pixel circuit may further include a reset circuit or the like ifrequired.

For example, as shown in FIG. 1A, the display panel 10 may furtherinclude a data driving circuit 6 and a gate driving circuit 7, which areconnected to the sub-pixel regions 100 through the data lines 12 and thegate lines 11 respectively. The data driving circuit provides a datasignal; and the gate driving circuit provides a scanning signal and mayfurther provide various control signals, power signals, and the like.

For example, each of the sub-pixel regions 100 includes a plurality ofsub-pixels, each sub-pixel including a light emitting structure 110 thatemits light of a different color, thereby achieving color display. Forexample, one sub-pixel region 100 includes three sub-pixels of RGB, andthe three sub-pixels include three light emitting structures 110 thatemit red, green, and blue light respectively.

As shown in FIG. 2, the display panel 10 includes a substrate 101 onwhich the plurality of sub-pixel regions 100 are disposed. The displaypanel 10 further includes a photosensitive region 200 disposed on thesubstrate 101, and the photosensitive region 200 is configured to senselight emitted by the light emitting structure 110 and reflected by afinger detected on the surface of the display panel 10, therebyrealizing fingerprint recognition function or touch sensing function.The photosensitive region 200 includes a photosensitive thin filmtransistor 201, which may convert an optical signal into an electricalsignal to implement functions such as fingerprint recognition or touchsensing.

Taking the photosensitive region implementing a fingerprint recognitionfunction as an example, in normal operation, the light emitted by thelight emitting structure 110, after being reflected by the surface of afinger 130, is received by the photosensitive thin film transistor 201in the photosensitive region 200 and converted into an electricalsignal. Since the valley of the fingerprint (a recessed surface) and theridge of the fingerprint (a convex surface) for the finger 130 havedifferent light reflectivities, light of different intensities isreflected, thereby generating electrical signals of differentmagnitudes. The photosensitive region 200 transmits the electricalsignals to an external processing circuit (e.g., a fingerprintprocessing chip, not shown) for analysis to obtain a fingerprint imageof the surface of the finger, the fingerprint image being further usedfor fingerprint recognition. For example, each of a plurality ofphotosensitive regions 200 in the fingerprint recognition area 30receives light reflected by a corresponding region of the finger 130 tocollect a fingerprint image of the corresponding region, and thecollected fingerprint images are then pieced into a complete fingerprintimage.

For example, in the fingerprint recognition area 30 of the display area20, each of the sub-pixel regions 100 corresponds to a display pixel,which may comprise three sub-pixels in a typical embodiment.Accordingly, each sub-pixel region is configured with one photosensitiveregion 200, that is, the display panel 10 includes a plurality ofphotosensitive regions 200 each in a one-to-one relation with one of theplurality of sub-pixel regions 100, i.e. a display pixel, and thephotosensitive regions 200 themselves are also arranged in an array,forming an image sensor to capture a fingerprint image. Each of thephotosensitive regions 200 is configured to sense light emitted from thecorresponding sub-pixel region 100 and reflected by the detected finger.

Referring to FIG. 3A, a sub-pixel region 100 in the fingerprintrecognition area 30 includes three sub-pixels of RGB. The threesub-pixels include three light emitting structures that emit red, green,and blue light respectively, and a photosensitive region S is disposedin the sub-pixel region. Each sub-pixel has a size substantially equalto a size of the photosensitive region.

According to an embodiment of the present disclosure, the display panelincludes: a substrate; and an array of pixels on the substrate, eachpixel having a sub-pixel region and a photosensitive region, wherein thesub-pixel region includes a light emitting structure; the photosensitiveregion is configured to sense light emitted by the light emittingstructure and reflected by a finger; and the photosensitive regionincludes a photosensitive thin film transistor having a vertical channelwith respect to the substrate.

As shown in FIG. 2, each sub-pixel of the sub-pixel region 100 furtherincludes a first transistor 120 in direct electrical connection with thelight emitting structure 110. The first transistor may be, for example,a driving transistor for driving the light emitting structure 110 toemit light in the pixel circuit, a light emitting control transistorcontrolling flow of the current that drives the light emitting element110 to emit light, or the like, which is not limited by the embodimentsof the present disclosure.

For example, the display panel 10 further includes an insulating layer140. With respect to the substrate 101, the photosensitive thin filmtransistor 201 is disposed under the insulating layer 140 (i.e. theinsulating layer is disposed over the photosensitive thin filmtransistor), and the light emitting structure 110 is disposed over theinsulating layer 140. This structure allows the photosensitive thin filmtransistor 201 to be formed before the light emitting structure 110.Since the light emitting structure 110 generally includes an organicmaterial, which has limited temperature tolerance, compared with formingthe photosensitive thin film transistor after or simultaneously with theformation of the light emitting structure, the photosensitive thin filmtransistor is formed before the formation of the light emittingstructure such that the fabrication process of the photosensitive thinfilm transistor 201 is not restricted by the temperature tolerance ofthe light emitting structure 110 and can be more flexible. For example,the insulating layer 140 is configured as a planarization layer suchthat the light emitting structure 110 is formed on a flat surface.Meanwhile, this is advantageous in increasing the area occupied by thelight emitting structure 110 and improving the display effect of thedisplay panel.

As shown in FIG. 2, the photosensitive thin film transistor 201 includesa gate electrode 202, a gate insulating layer 203, a first electrode204, an active layer 205, and a second electrode 206, which aresequentially formed over the substrate 101. The photosensitive thin filmtransistor 201 has a vertical channel with respect to the substrate 101,that is, the direction of the channel from the source to the drain isperpendicular to the plate surface of the substrate 101. Compared withthe thin film transistor having a horizontal channel, the verticalchannel structure allows the photosensitive area of the photosensitivethin film transistor 201 (that is, the planar area of the secondelectrode 206) and the channel length to be independent from each other,so that it is possible to have a shorter channel length with a largerphotosensitive area, thereby improving the light responsivity and thesignal-to-noise ratio of the photosensitive region 200.

The light emitting structure 110 includes a first electrode 111, alight-emitting layer 112, and a second electrode 113. One of the firstelectrode 111 and the second electrode 113 is an anode, and the other isa cathode. The light-emitting layer 112 may be an organic light-emittinglayer or a quantum dot light-emitting layer. For example, the lightemitting structure 110 may include a hole injection layer, a holetransport layer, an electron injection layer, an electron transportlayer, or the like, besides the light-emitting layer 112. For example,when the light-emitting layer 112 is an organic light-emitting layer, itmay be made of a polymer light-emitting material or a small moleculelight-emitting material. The light emitting structure 110 is a topemission structure with the first electrode 111 being reflective and thesecond electrode 113 being transmissive or semi-transmissive. Forexample, the first electrode 111, which serves as an anode, is made of ahigh work function material, such as an ITO/Ag/ITO laminate structure;and the second electrode 113, which serves as a cathode, is made of alow work function material, such as a semi-transmissive metal or metalalloy, e.g., an Ag/Mg alloy material.

The first transistor 120 includes a gate 121, an active layer 122, asource 123, and a drain 124. The type, material, and/or structure of thefirst transistor 120 are not limited by the embodiments of the presentdisclosure. For example, it may be a top gate type, a bottom gate type,or the like. The active layer 122 of the first transistor 120 may bemade of amorphous silicon or polycrystalline silicon (low-temperaturepolycrystalline silicon or high temperature polycrystalline silicon), anoxide semiconductor (e.g., IGZO), etc., and the first transistor 120 maybe N-type or P-type.

The active layer 205 of the photosensitive thin film transistor 201includes a photosensitive layer 2051, which generates photo-generatedcarriers with light irradiation. The photo-generated carriers arecollected by a photo-sensing circuit (not shown) to be converted into anelectrical signal, which is output to an external processing circuit tobe analyzed to obtain a fingerprint image.

For example, the photosensitive layer 2051 is made of a semiconductormaterial, and can generate an electric charge in the presence of thegate electric field. In this case, the photosensitive thin filmtransistor 201 has both a photosensitive function and a switchingfunction.

For example, a material of the photosensitive layer 2051 ispoly(3-hexylthiophene) (P3HT), which is an organic material having bothphotosensitivity and semiconductor properties. To improve thephotosensitivity of the P3HT material, it may be doped with[6,6]-phenyl-C 61-butyric acid methyl ester (PCBM) to form aphotosensitive layer 2051 comprising a material of P3HT and PCBMcomposite.

For example, in order to increase the signal intensity outputted by thephotosensitive thin film transistor 201, the active layer 205 mayfurther be provided with a semiconductor layer 2052. For example, asshown in FIG. 2, the semiconductor layer 2052 is disposed between thephotosensitive layer 2051 and the first electrode 204. The semiconductorlayer 2052 is configured to generate carriers under the electric fieldgenerated by the gate voltage, thereby increasing the signal intensityoutput from the photosensitive thin film transistor 201. For example,the semiconductor layer 2052 may be disposed between the photosensitivelayer 2051 and the second electrode 206. In his case, the semiconductorlayer 2052 is made of a light transmissive material so that thephotosensitive layer 2051 can receive and sense the light.

For example, in order to improve the uniformity and stability of thephotosensitive thin film transistor 201, the semiconductor layer 2052 ismade of an amorphous semiconductor material. For example, the materialof the semiconductor layer 2052 is an organic semiconductor material,such as dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) orpentacene, or an inorganic semiconductor material, such as amorphoussilicon or an oxide semiconductor (e.g., IGZO). For example, thematerial of the first electrode 204 is a porous semiconductor electrodematerial. On one hand, the porous semiconductor electrode material issparse and does not completely shield the electric field formed by thevoltage applied to the gate electrode 202; on the other hand, thesemiconductor electrode material has a moderate electronic density ofstates (DOS) such that it can conduct electricity, and, at the sametime, allows the gate electrode 202 to regulate the charge injection tothe active layer 205 by the first electrode 204. This property of thematerial allows control of the operational state of the photosensitivethin film transistor 201 by applying a voltage to the gate electrode.For example, the material of the first electrode 204 is carbonnanotubes. A plurality of carbon nanotubes is arranged to form a sparsestructure, and the adjacent carbon nanotubes have a gap therebetween,which may reduce the shielding of the electric field formed by thevoltage applied to the gate electrode; in the meantime, the carbonnanotubes, which are a semiconductor material having a moderateelectronic density of states, allow the gate electrode 202 to regulatethe charge injection to the active layer 205 by the first electrode 204while conducting electricity, thereby allowing control of theoperational state of the photosensitive thin film transistor 201 byapplying a voltage to the gate electrode 202.

For example, the material of the second electrode 206 is a transparentconductive material through which the reflected light received reachesthe active layer 205. By increasing the planar area of the secondelectrode 206, the photosensitive area of the photosensitive thin filmtransistor 201 can be increased, thereby improving the luminous flux andsignal-to-noise ratio of the photosensitive thin film transistor 201.For example, the material of the second electrode 206 is an ultra-thinmetal, carbon nanotubes, graphene, silver nanowires, or transparentoxide conductive material such as indium tin oxide (ITO), indium galliumzinc oxide (IGZO) or the like.

For example, the photosensitive region 200 further includes a firstelectrode lead 2040 electrically connected to the first electrode 204 ofthe photosensitive thin film transistor 201, the first electrode 204including a first portion 2041 and a second portion 2042. The firstportion 2041 is disposed on and covers the first electrode lead 2040with respect to the substrate 101 to achieve lapping (electricalconnection), and the second portion 2042 and the first electrode lead2040 are arranged side by side with respect to the substrate 101, thatis, the second portion 2041 is disposed adjacent to the first electrodelead 2040 on the gate insulating layer 203.

For example, the photosensitive region 200 further includes a secondelectrode lead 2060 electrically connected to the second electrode 206of the photosensitive thin film transistor 201. The first electrode lead2040 and the second electrode lead 2060 are used to electrically connectthe first electrode 204 and the second electrode 206 to other elementsrespectively.

For example, the sub-pixel region 100 further includes a firstconductive layer 125 disposed above the gate 121 of the first transistor120 and spaced apart from the gate 121 to form a first capacitor, thatis, an electrode of the first capacitor and the gate 121 of the firsttransistor are electrically connected and integrally formed to store ormaintain the electrical level of the gate 121.

For example, the gate 121 of the first transistor 120, disposed in thesame layer as the gate electrode 202 of the photosensitive thin filmtransistor 201, is insulated from the gate electrode 202.

For example, the second electrode lead 2060 is disposed in the samelayer as the source 123 or the drain 124 of the first transistor 120.

For example, the first electrode lead 2040 disposed in the same layer asthe first conductive layer 125 is insulated from the first conductivelayer 125.

It should be noted that “disposed in the same layer” in the embodimentsof the present disclosure means that two or more structures are formedby the same patterning process using the same material, and it does notnecessarily mean having the same height or being formed on the samesurface.

It should also be noted that since the source 123 and the drain 124 ofthe first transistor 120 are physically symmetrical as shown in FIG. 2,the two may be interchangeable according to circuit connections.

For example, the photosensitive thin film transistor 201 is disposedabove the active layer 122 of the first transistor 120 with respect tothe substrate 101, i.e. the photosensitive thin film transistor isdistal from the substrate relative to an active layer of the firsttransistor. Since the active layer 122 generally occupies a large areain the layout, the photosensitive thin film transistor 201 according tothe embodiments of the present disclosure is arranged above the activelayer 122 to avoid the photosensitive thin film transistor 201 squeezingthe space of the active layer 122, thereby facilitate layout design.

For example, the display panel 10 further includes a filter layer 160disposed on a side of the second electrode 206 of the photosensitivethin film transistor 201 away from the substrate 101 and covering thephotosensitive thin film transistor 201. That is, the filter layer isover the second electrode of the photosensitive thin film transistor.For example, the filter layer 160 is disposed on the insulating layer140. The filter layer 160 is configured such that the photosensitivelayer 2051 of the photosensitive thin film transistor 201 only senseslight of a certain color, thereby improving the recognition accuracy ofthe photosensitive thin film transistor 201. Since the fingerprint isidentified by detecting light intensity in fingerprint recognitiontechnology, the uniformity of the intensity of the light emitted by thelight source affects the accuracy of the recognition. By providing thefilter layer 160, the light received by the photosensitive thin filmtransistor 201 is filtered to be monochromatic, that it, the receivedlight is filtered and become light of a same color as that of the lightemitted by a sub-pixel in the sub-pixel region, thereby preventingdifferences in light intensity resulted from the received light beingemitted by different sub-pixels. For example, the color of the filterlayer 160 is one of red, green, and blue. For example, the material ofthe filter layer 160 is a resin material or the like.

For example, the photosensitive region 200 further includes a secondcapacitor 207, and the second capacitor 207 includes a first electrode208 and a second electrode 209. As shown in FIG. 2, the first electrode208 is disposed in the same layer as the gate electrode 202 of thephotosensitive thin film transistor 201, and is insulated from the gateelectrode 202; and the second electrode 209 is disposed in the samelayer as the second electrode lead 2060 of the photosensitive thin filmtransistor 201, and is electrically connected to the second electrodelead 2060. For example, the second electrode 209 of the second capacitor207 is integrally formed with the second electrode lead 2060 of thephotosensitive thin film transistor 201. In one example, the secondcapacitor 207 and the photosensitive thin film transistor 201 form aphoto-sensing circuit 210 shown in FIG. 3B.

As shown in FIG. 3B, the photo-sensing circuit 210 according to anembodiment of the present disclosure includes the photosensitive thinfilm transistor 201 and the second capacitor 207. The second electrode206 of the photosensitive thin film transistor 201 and the secondelectrode 209 of the second capacitor 207 are connected electrically.The first electrode 204 of the photosensitive thin film transistor 201is electrically connected to a processing circuit 211, and the firstelectrode 204 is connected to the external processing circuit 211through the first electrode lead 2040 (read signal line). The gateelectrode 202 of the photosensitive thin film transistor 201 isconnected to a control signal VG through a scanning signal line. Thefirst electrode 208 of the second capacitor 207 may be connected to afixed potential. For example, the first electrode 208 of the secondcapacitor 207 is grounded.

A working process of the photo-sensing circuit 210 includes thefollowing. In the reset phase, the control signal VG is an ON signal;the photosensitive thin film transistor 201 is turned on; and theprocessing circuit 211 writes a reset signal to the second capacitor 207via the photosensitive thin film transistor 201 to reset the secondcapacitor 207. In the photosensitive phase, the control signal VG is anOFF signal; the photosensitive thin film transistor 201 is turned off;the photosensitive layer 2051 generates photo-generated carriers withthe irradiation of the reflected light; the processing circuit 211applies a bias voltage to the first electrode 204 via the read thesignal line, to generate an electric field between the first electrode204 and the second electrode 206 of the photosensitive thin filmtransistor 201; under the electric field, the photo-generated carriersare transported to and gathered on the second electrode 209 of thesecond capacitor 207 such that the second capacitor is charged and adata voltage Vdata is generated at the second electrode 209. In thedetection phase, the control signal VG is an ON signal; thephotosensitive thin film transistor 201 is turned on; and the processingcircuit 211 reads from the photosensitive thin film transistor 201 viathe read signal line the data voltage Vdata stored in the secondcapacitor 207, and analyzes it to form a fingerprint image.

In the above photo-sensing circuit, the photosensitive thin filmtransistor 201 has both a photosensitive function and a switchingfunction, and thus a switching transistor may be omitted compared withthe conventional photo-sensing circuit, which not only simplifies thecircuit, but also saves layout area.

For example, the photo-sensing circuit 210 may detect visible light orinfrared light, and the data voltage obtained from the detection andacquisition by the photo-sensing circuit 210 may be read by theprocessing circuit 211 for further processing to obtain a fingerprintimage. The fingerprint image may be used for applications such as systemunlocking, mobile payments, and the like. The processing circuit 211 maybe a digital signal processor (DSP), a central processing unit, etc.,and may also include a storage device if needed. The specificimplementations of the photo-sensing circuit 210 and the processingcircuit 211 are not limited by the embodiments of the presentdisclosure.

It should be understood by those skilled in the art that a switchingelement may be additionally provided to form a photo-sensing circuitwith the photosensitive thin film transistor 201. FIG. 3C shows aschematic view of another photo-sensing circuit according to anembodiment of the present disclosure. As shown, the photo-sensingcircuit 310 includes a photosensitive thin film transistor 201, aswitching transistor 301, and a second capacitor 207. The gate electrodeof the photosensitive thin film transistor 201 is electrically connectedto one of the first electrode 204 and the second electrode 206, and isalso connected to a fixed potential, such that the photosensitive thinfilm transistor 201 is kept in an OFF state. For example, the gateelectrode of the thin film transistor 201 is electrically connected tothe first electrode 204, and is grounded in FIG. 3C. The first electrodeof the switching transistor 301 is connected to the processing circuit211; the second electrode of the switching transistor 301 iselectrically connected to the second electrode 206 of the photosensitivethin film transistor 201; and the gate electrode of the switchingtransistor 301 is connected to the control signal VG.

A working process of the photo-sensing circuit 310 includes thefollowing. In the reset phase, the control signal VG is an ON signal;the switching transistor 301 is turned on; and the processing circuit211 writes a reset signal to the second capacitor 207 to reset thesecond capacitor 207. In the photosensitive phase, the control signal VGis an OFF signal; the switching transistor 301 is turned off; and thephotosensitive thin film transistor 201 generates photo-generatedcarriers with the irradiation of the reflected light and charges thesecond capacitor 207, causing the second capacitor 207 to generate andstore a data voltage Vdata. In the detection phase, the control signalVG is an ON signal; the switching transistor 301 is turned on; and theprocessing circuit 211 reads the data voltage Vdata stored in the secondcapacitor 207 through the photosensitive thin film transistor 201, andthen analyzes it to form a fingerprint image. The details are notrepeated here.

For example, the photosensitive region 200 may also be used to implementtouch sensing, that is, to sense a user's touch. For example, when theuser's finger touches the display panel 10, the light emitted by thelight emitting structure 110 is reflected by the surface of the fingerand then received by the photosensitive thin film transistor 201 of thephotosensitive region 200, which converts it into an electrical signal.The external circuit, by detecting the electrical signal, may determinethe touch of the finger, the direction of movement, etc., which are notdescribed in details here.

According to an embodiment of the present disclosure, a method offabricating the display panel 10 is provided, the method comprising:providing a substrate; and forming an array of pixels on the substrate,each pixel having a sub-pixel region and a photosensitive region;wherein the sub-pixel region comprises a light emitting structure; thephotosensitive region is configured to sense light emitted by the lightemitting structure and reflected by a finger; and the photosensitiveregion comprises a photosensitive thin film transistor having a verticalchannel with respect to the substrate.

FIGS. 4A-4E are diagrams illustrating a process of a method offabricating a display panel according to an embodiment of the presentdisclosure. The method for fabricating the display panel according tothe embodiment of the present disclosure will be exemplified in thefollowing with reference to FIGS. 4A-4E and FIG. 2. In the embodimentsof the present disclosure, the same components are denoted by the samereference numerals.

For example, the manufacturing method includes the following stepsS41-S45.

Step S41: as shown in FIG. 4A, forming a gate electrode 202 of aphotosensitive thin film transistor 201.

For example, a first conductive material layer is formed on a substrate101 and a patterned process is performed on the first conductivematerial layer to form the gate electrode 202.

For example, a gate 121 of a first transistor 120 may be formed togetherwhile forming the gate electrode 202.

For example, in order to form the first transistor 120, a buffer layer102, an active layer 122 of the first transistor, and a gate insulatinglayer 103 may be sequentially formed on the substrate 101 before formingthe gate electrode 202.

For example, a first electrode 208 of a first capacitor 207 may also beformed together while forming the gate electrode 202.

For example, the conductive material used to form the gate electrode 202may be a metal such as gold (Au), silver (Ag), copper (Cu), aluminum(Al), molybdenum (Mo), magnesium (Mg), tungsten (W), or the like, analloy material in which the metal is combined, or a conductive metaloxide material such as indium tin oxide (ITO), indium zinc oxide (IZO),zinc oxide (ZnO), zinc aluminum oxide (AZO), or the like.

For example, the substrate 101 may be an inorganic substrate (such asglass, quartz, sapphire, silicon wafer, etc.) or an organic flexiblesubstrate (such as polyimide (PI), polyethylene terephthalate (PET),polycarbonate, polyethylene, polyacrylate, polyetherimide,polyethersulfone, etc.), which the embodiments of the present disclosureinclude, but are not limited to.

For example, the conductive material layer is patterned by aconventional photolithography process to form the gate electrode 202 ofthe thin film transistor 201, the gate 121 of the first transistor 120,and a first electrode 208 of a second capacitor 207, which are insulatedfrom one another.

Step S42: as shown in FIG. 4B, sequentially forming a gate insulatinglayer 203, a first electrode lead 2040, and a first electrode 204 of thephotosensitive thin film transistor 201 on the gate electrode 202.

For example, the gate insulating layer 203 may be an inorganicinsulating material, which may be an oxide of silicon, a nitride ofsilicon or an oxynitride of silicon such as silicon oxide, siliconnitride, silicon oxynitride or the like, or may be an insulatingmaterial including metallic elements such as aluminum oxide, titaniumnitride, or the like. For example, the gate insulating layer 203 mayalso be an organic insulating material such as acrylic acid orpolymethyl methacrylate (PMMA).

For example, the first electrode lead 2040 is formed by forming a secondconductive material layer and patterning the second conductive materiallayer.

For example, in order to cooperate with the pixel circuit forming thesub-pixel region, a first conductive layer 125 in the pixel circuit isalso formed together while forming the first electrode lead 2040, andthe first conductive layer 125 may be spaced apart from the gate 121 toform a first capacitor.

For example, the first electrode 204 is formed by forming a thirdconductive material layer and patterning the third conductive materiallayer. For example, the first electrode 204 includes a first portion2041 overlaying the first electrode lead 2040 with respect to thesubstrate 101 to form a lapped structure, and a second portion 2042disposed side by side with the first electrode lead 2040 with respect tothe substrate 101. That is, the second portion 2042 is formed adjacentto the first electrode lead 2040 on the gate insulating layer 203. Forexample, the third conductive material layer is formed by a coatingprocess, and the patterning process is dry etching.

For example, the third conductive material layer is a poroussemiconductor electrode material. On one hand, the porous semiconductorelectrode material is sparse and does not completely shield the electricfield formed by applying a voltage to the gate electrode 202; on theother hand, the porous semiconductor electrode material has a moderateelectronic density of states (DOS) such that it may conduct electricity,and, at the same time, allows the gate electrode 202 to regulate thecharge injection to the active layer 205 by the first electrode 204.This property of the material allows control of the operational state ofthe photosensitive thin film transistor 201 by applying a voltage to thegate electrode. For example, the material of the first electrode 204 iscarbon nanotubes. A plurality of carbon nanotubes is arranged to form asparse structure. The carbon nanotubes not only have a pore-likestructure, but also have gaps therebetween, which may reduce theshielding of the electric field formed by the voltage applied to thegate electrode; in the meantime, the carbon nanotubes, which are asemiconductor material having a moderate electronic density of states,allow the gate electrode 202 to regulate the charge injection to theactive layer 205 by the first electrode 204 while conductingelectricity, thereby allowing control of the operational state of thephotosensitive thin film transistor 201 by applying a voltage to thegate electrode 202.

Step S43: forming an active layer 205 on the first electrode 204 asshown in FIG. 4C.

For example, in order to make the active layer 205 have a flatinterface, the active layer 205 may be formed only on the second portion2042 of the first electrode 204.

The active layer 205 includes a photosensitive layer 2051 that generatesphoto-generated carriers with irradiation of light, thereby convertingthe optical signal into the electrical signal. The photo-generatedcarriers are collected by a photo-sensing circuit, and then areconverted into electrical signals output to an external processingcircuit for analysis to obtain a fingerprint image.

For example, the photosensitive layer is a semiconductor material, andcan generate an electric charge in the presence of the gate electricfield. In this case, the photosensitive thin film transistor has both aphotosensitive function and a switching function.

For example, in order to increase the signal intensity outputted by thephotosensitive thin film transistor 201, the active layer 205 mayfurther be provided with a semiconductor layer 2052. For example, asshown in FIG. 2, the semiconductor layer 2052 is disposed between thephotosensitive layer 2051 and the first electrode 204. The semiconductorlayer 2052 is configured to generate carriers under the electric fieldgenerated by the gate voltage, thereby increasing the signal intensityoutput from the photosensitive thin film transistor 201.

For example, the semiconductor layer 2052 may be disposed between thephotosensitive layer 2051 and the second electrode 206. In his case, thesemiconductor layer 2052 is made of a light transmissive material sothat the photosensitive layer 2051 can receive and sense the light.

For example, a material of the photosensitive layer 2051 ispoly(3-hexylthiophene) (P3HT), which is an organic material having bothphotosensitivity and semiconductor properties. To improve thephotosensitivity of the P3HT material, it may be doped with[6,6]-phenyl-C 61-butyric acid methyl ester (PCBM), that is, thephotosensitive layer 2051 is formed using a material of P3HT and PCBMcomposite.

For example, in order to improve the uniformity and stability of thephotosensitive thin film transistor 201, the semiconductor layer 2052 ismade of an amorphous semiconductor material. For example, thesemiconductor layer 2052 is made of an organic semiconductor material,such as dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) orpentacene.

For example, a semiconductor material layer and a photosensitivematerial layer are sequentially formed on the second portion 2042 of thefirst electrode 204, and the semiconductor material layer and thephotosensitive material layer are patterned by a patterning process toform the photosensitive layer 2052 and the semiconductor layer 2051. Forexample, the patterning process includes dry etching to avoid corrosionand damage to the semiconductor material layer and the photosensitivematerial layer by the wet etching process.

Step S44: as shown in FIG. 4D, sequentially forming an interlayerinsulating layer 105 and a second electrode 206 on the active layer 205.

An opening 1050 is formed in the interlayer insulating layer 105 at aposition corresponding to the active layer 205 to expose at least aportion of the active layer 205, and a second electrode 206 is formed tocover the active layer 205 exposed by the opening.

For example, a source contact hole 1230 and a drain contact hole 1240 ofthe first transistor are formed while forming the opening 1050, whichexpose the source region and the drain region of the active layer of thefirst transistor, respectively.

For example, the second electrode 206 is formed of a transparentconductive material through which the reflected light received reachesthe active layer 205. By increasing the planar area of the secondelectrode 206, the photosensitive area of the photosensitive thin filmtransistor 201 can be increased, thereby improving the luminous flux andsignal-to-noise ratio of the photosensitive thin film transistor 201.For example, the material of the second electrode 206 is an ultra-thinmetal, carbon nanotubes, graphene, silver nanowires, or transparentoxide conductive material such as indium tin oxide (ITO), indium galliumzinc oxide (IGZO) or the like.

Step S45: forming a second electrode lead 2060.

For example, as shown in FIG. 4E, the second electrode lead 2060 may bedirectly formed on and overlapped with the second electrode 206, thatis, no intermediate layer is formed between the second electrode lead2060 and the second electrode 206. However, it is possible to form aninsulating layer between the second electrode lead 2060 and the secondelectrode 206, where the second electrode lead 2060 is electricallyconnected to the second electrode 206 through a via hole in theinsulating layer, which is not limited by the embodiments of the presentdisclosure.

For example, a source or a source electrode 123 and a drain or a drainelectrode 124 of the first transistor are formed together while thesecond electrode lead 2060 is formed, that is, the second electrode lead2060, the source 123 and the drain 124 of the first transistor areformed by the same patterning process with the same conductive material.The source 123 and the drain 124 of the first transistor areelectrically connected to the active layer of the first transistorthrough the source contact hole 1230 and the drain contact hole 1240,respectively.

For example, a second electrode 209 of the second capacitor 207electrically connected to the second electrode lead 2060 is formed atthe same time as the second electrode lead 2060. For example, as shown,the second electrode 209 is integrally formed with the second electrodelead 2060.

Accordingly, the above-described photosensitive thin film transistor 201having a vertical channel is formed.

Then, an insulating layer 140 is formed, and a first electrode 111, alight emitting layer 112, and a second electrode 113 of a light emittingstructure 110 are sequentially formed to form the light emittingstructure 110.

For example, a pixel defining layer is formed before the light emittinglayer 112 is formed. Since the pixel defining layer is generally opaque,an opening in the pixel defining layer is formed at a positioncorresponding to the photosensitive thin film transistor 201 such thatthe light is not blocked from radiating the photosensitive thin filmtransistor. For example, the opening may be formed simultaneously withan aperture of the pixel defining layer corresponding to the lightemitting structure.

For example, an encapsulation layer may be formed on the array substrateobtained above to seal the light emitting structure, details of whichare not described herein.

The method of fabricating a display panel according to the embodimentsof the present disclosure includes forming a photosensitive region byusing a photosensitive thin film transistor having a vertical channel.The photosensitive thin film transistor having a relatively largephotosensitive area (or a large aperture ratio) and a relatively shortchannel length. Thus, the light responsivity and signal-to-noise ratioof the display panel may be improved. In at least one embodiment, thephotosensitive thin film transistor may be compatible with thefabrication process of the pixel circuit, for example, in thefabrication method according to the above embodiments, the formation ofthe photosensitive thin film transistor requires only three additionalpatterning processes of forming the first electrode 204, the activelayer 205, and the second electrode 206, and other structural layers maybe fabricated together with the structures of the pixel circuit, therebysimplifying the fabrication process and reducing the cost.

Various embodiments and/or examples are disclosed to provide exemplaryand explanatory information to enable a person of ordinary skill in theart to put the disclosure into practice. Features or componentsdisclosed with reference to one embodiment or example are alsoapplicable to all embodiments or examples unless specifically indicatedotherwise.

Although the disclosure is described in combination with specificembodiments, it is to be understood by the person skilled in the artthat many changes and modifications may be made and equivalentreplacements may be made to the components without departing from ascope of the disclosure. Embodiments may be practiced in other specificforms. The described embodiments are to be considered in all respectsonly as illustrative and not restrictive.

The invention claimed is:
 1. A display panel comprising: a substrate;and an array of pixels on the substrate, each pixel having a sub-pixelregion and a photosensitive region, wherein the sub-pixel regioncomprises a light emitting structure; the photosensitive region isconfigured to sense light emitted by the light emitting structure andreflected by a finger; the photosensitive region comprises aphotosensitive thin film transistor having a vertical channel withrespect to the substrate; the photosensitive thin film transistorcomprises a gate electrode, a gate insulating layer, a first electrode,an active layer, and a second electrode sequentially formed over thesubstrate; and the active layer comprises a photosensitive layer.
 2. Thedisplay panel according to claim 1, further comprising an insulatinglayer over the photosensitive thin film transistor, wherein the lightemitting structure is disposed over the insulating layer.
 3. The displaypanel according to claim 1, wherein the photosensitive layer comprises amaterial of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl-C 61-butyricacid methyl ester (PCBM) composite.
 4. The display panel according toclaim 1, wherein the active layer further comprises a semiconductorlayer between the photosensitive layer and the first electrode.
 5. Thedisplay panel according to claim 4, wherein the semiconductor layercomprises dinaphtho[2,3-b:2′,3′-f]thieno[3,2-b]thiophene (DNTT) orpentacene.
 6. The display panel according to claim 1, wherein a materialof the first electrode is a porous semiconductor electrode material. 7.The display panel according to claim 6, wherein a material of the firstelectrode is carbon nanotubes.
 8. The display panel according to claim1, wherein a material of the second electrode is a transparentconductive material.
 9. The display panel according to claim 1, whereinthe photosensitive region further comprises a first electrode leadelectrically connected to the first electrode; and the first electrodecomprises a first portion and a second portion, the first portioncovering the first electrode lead with respect to the substrate, thesecond portion and the first electrode lead being arranged side by sidewith respect to the substrate.
 10. The display panel according to claim1, wherein the sub-pixel region further comprises a first transistor,and a source or a drain of the first transistor is electricallyconnected to a first electrode of the light emitting structure.
 11. Thedisplay panel according to claim 10, wherein a gate of the firsttransistor is in a same layer as the gate electrode of thephotosensitive thin film transistor.
 12. The display panel according toclaim 10, wherein the photosensitive region further comprises a secondelectrode lead electrically connected to the second electrode of thephotosensitive thin film transistor, and the second electrode lead is ina same layer as the source or the drain of the first transistor.
 13. Thedisplay panel according to claim 10, wherein the photosensitive thinfilm transistor is distal from the substrate relative to an active layerof the first transistor.
 14. The display panel according to claim 1,wherein the sub-pixel region comprises a plurality of sub-pixels, eachsub-pixel having a size substantially equal to a size of thephotosensitive region.
 15. The display panel according to claim 1,further comprising a filter layer over the second electrode of thephotosensitive thin film transistor, the filter layer covering thephotosensitive thin film transistor.
 16. A method of fabricating adisplay panel comprising: providing a substrate; and forming an array ofpixels on the substrate, each pixel having a sub-pixel region and aphotosensitive region; wherein the sub-pixel region comprises a lightemitting structure; the photosensitive region is configured to senselight emitted by the light emitting structure and reflected by a finger;the photosensitive region comprises a photosensitive thin filmtransistor having a vertical channel with respect to the substrate; thephotosensitive thin film transistor comprises a gate electrode, a gateinsulating layer, a first electrode, an active layer, and a secondelectrode sequentially formed over the substrate; and the active layercomprises a photosensitive layer.
 17. The method according to claim 16,further comprising: forming an insulating layer over the photosensitivethin film transistor; and forming the light emitting structure over theinsulating layer.
 18. The method according to claim 16, furthercomprising: forming the photosensitive thin film transistor bysequentially forming a gate electrode, a gate insulating layer, a firstelectrode, an active layer, and a second electrode over the substrate.